Process for hydrocarbon conversion



amt May 30.1944

2,350,159 rnocsss ron rmmocannon CONVERSION mm; o. Folkins, Skoliie, and Carlisle M. Thacker', Highland Park, 111., assignors to The Pure Oil Company, Chicago, Ill., a corporation of Ohio Application October 19, .1942, Serial No. 462,500

7 Claims.

This invention relates to a method of converting hydrocarbons to hydrocarbons of lower boiling point or to hydrocarbons containing less hydrogeri in the molecule and is particularly concerned with conversion of hydrocarbons containing 3 or more carbon atoms in the molecule.

It is well known that hydrocarbons crack at elevated temperatures ranging upward from.

about 700 F. to produce hydrocarbons of greater unsaturation and/or hydrocarbons of lower boiling point. It is also known that the rate of cracking is proportional to the temperature.

We have discovered that at any particular cracking temperature the rate of cracking can be greatly accelerated by contacting the hydrocarbons undergoing conversion with a mixture of an aliphatic halide and mercury.

One of the objects of the invention is to provide an improved process for cracking hydrocarbons.

Another object of the invention is to provide a process for homogeneous catalysis of hydrocarbon crocking reactions.

A still further object the invention is to provide an accelerator or sensitizer for catalyzing cracking reactions.

Other objects of the invention will become manifest from the following detailed description of the invention considered in conjunction with the accompanying drawing of which the single figure is a diagrammatic side elevational view.

Referring to the drawing, l indicates the feed line through which hydrocarbons are charged to the cracking system by means of pump 3. The process is designed to crack propane, butane, or any mixture of Ca and C4 hydrocarbons as well as higher boiling hydrocarbons such as those within the gasoline, kerosene, gas oil or residuum boiling range. It will be understood that in the event the charging stock is composed of normally gaseous hydrocarbons, these gases may be charged to the system either in the liquid or gaseous A state. When charged in the gaseous state a compressor will'be substituted for the pump 3 The charging stock is pumped or forced through the preheater' or vaporizer 5 where it is heated or vaporized at a temperature below but preferably close to the desired cracking temperature. The cracking temperature will vary with the nature of the charging stock and the nature of the products which it is desired to produce, but in general will range from approximately 700 F. to 1400 F. The lower boiling hydrocarbons will in general require drocarbons, but it will be understood that temperatures for converting the higher boiling hydrocarbons may be just as high as those used for converting the lower boiling hydrocarbons where it is desired to make low boiling unsaturated products such as ethylene, propylene, butylene and butadiene. Even higher temperatures may be resorted to when necessary, as for ex- In genample in the manufacture of acetylene. eral we prefer to keep the temperature in the preheater or vaporizer 5 below that at which rapid conversion of the hydrocarbons takes place Mercury is charged to the cracking system through the line I by means of pump 9 and through vaporizer H where it is heated to a temperature sufiicient to vaporize the mercury. This temperature will depend on the pressure at which the cracking system is operated. The vaporized mercury is then mixed with the preheated hydrocarbons in the line H and the mixture charged to preheater l5 where it is heated to the desired reaction temperature. The preheater may take the form of a coil located in a suitable furnace. The amount of mercury mixed with the hydrocarbons may vary widely, but from 6 to 10 mole per cent of mercury be ad on the hydrocarbons is sufiicient to produce the desired acceleration in conjunction with the aliphatic halide. Aliphatic'halide is charged to the system through line H by means of pump [9. The aliphatic halide is preferably first preheated and vaporized in 2| so that it may beinjected into the reaction zone in the form of a vapor. The temperature to which the alkyl halide is preheated will depend on the particular halide and the pressure conditions existing in the reaction zone, it being desired merely to vaporize the alkyl halide in vaporizer 2|. Any aliphatic halide which may be vaporized at reaction tem-"- perature can be used, but we prefer to use those which are liquid at ordinary atmospheric temperatures, vaporize without appreciable decomposition and contain 7 or less carbon atoms in the molecule. Saturated as well as unsaturated halides may be used such as ethyl iodide, ethylene di-bromide, propyl iodide, butyl fluoride, butyl chloride, 3-bromo propyne and 3-iodo propyne. The amount of halide used may vary within wide limits but we prefer to use from t;

to 10 mole per cent of halide based on the hydrocarbons charged.

The mixture of mercury vapor and hydrocarbons after being heated to the desired reaction temperature in a coil or heater l5 are charged to higher temperatures than the higher boiling hythe reactor-J3, which may take the form of a steel or refractory chamber, or of a. steel coil.

invention in a shorter period or a greater percentage conversion can be obtained in the same period of time.

The aliphatic halide in the vapor state may be injected'into the reactor through a series of parallel lines 25, 21, 29, and SI controlled by valves 33, 35, 31, and 39 at diflerent points in the reactor. It is advantageous to distribute the halide throughout the reactor in order to insure that halide is prevent during substantially all stages of the reaction.

The reaction products are withdrawn from the reactor through the line 4| and are sent to the recovery system to separate the various products therefrom. The recovery of the various reaction products forms no part of this invention and therefore will not be illustrated or described. It may, however, correspond to any known or con- TABLE 1 Decomposition of normal butane [Total pressure on system-750 mm. (spprox.)]

Run No.

Reactor temperature, C.:

0p 672 592 497 599 600 598 Middle.. 576 600 600 600 600 600 Bottom 574 699 598 597 599 597 Total gas flow .ftfi/lnz. 0. 994 0.998 1.000 0.994 1.020 0.995 110 B; flow. .ft.=/hr 0.994 0.9981.000 0.986 0. 989 0.979 Pressure Hg .millimeters. 0 0 0 4 0 v 4 Pressure CIHBI ..'do..-. 0 0 0 0 7. 5 7. 5 Vol. exit gas vol. inlet 04111 1. 014 1.052 1.060 1.064 1. 172 1.103 Yield it. unsats. per it. 04111 charged 0. 035 0. 067 0. 063 0. 065 0. 089 0. 165 Exitas, mol percent 7 1 0.9 0.8 0.9 0.6 1.3 0.9 Unsats 3.4 6.4 5.9 6. 1 7.0 14. 2

In all the runs normal butane was used as the charging stock. In those runs where mercury and/or ethyl iodide were used as sensitizers the quantity of mercury was used slightly in excess of mole per cent and the quantity of ethyl iodide was approximately 1 mole per cent. The extent of cracking which occurred is indicated by the yield of unsaturates per cubic foot of butane charged.

Run #1 was a blank run made'at a temperature of approximately 575 C. Because of the small amount of conversion which occurred at this temperature blank runs #2 and #3 were made at temperatures of approximately600 C. and the yield of 0.067 and 0.063 check fairly closely. Run

the yield of unsaturates was substantially the same as that obtained in the blank runs.

A run was then made using ethyl iodide as sensltizer at 600 C. and the yield of .089 unsaturates indicates that the ethyl iodide sensitized or 8.0- celerated the reaction to the extent of 40%. Run #6 was then made under -the same conditions using the combination or ethyl iodide and mercury as sensitizer and a yield of 0.165 cu. feet of unsaturates per cubic foot of butane was obtained, thus indicating an acceleration of the reaction of over 150 per cent.

Thus, it will be seen that the mixture of mercury and ethyl iodide greatly accelerated the cracking reaction. It will also be seen that although a small amount of dehydrogenation occurred the reaction was predominantly one ofsplitting of the butane molecule to form lower boiling unsaturated hydrocarbons.

Although we have demonstrated one way in which our invention may be carried out it should be understood that the manner and order of mixing the sensitizers with the hydrocarbonsundergoing reaction and the particular type of apparatus used may be varied. It should be also understood that a mixture of aliphatic halides may be used instead of a single halide.

The pressure under which the reaction is conducted may be sub-atmospheric, atmospheric or super-atmospheric. For example, where the purpose of the conversion reaction is to prepare acetylenes or dioleflns it may be desirable to use sub-atmospheric pressures. Where high boiling hydrocarbons are cracked to form gasoline it may be desirable to use 'high pressures of the order of those commonly used in purely thermal cracking processes. The conditions of both temperature and pressure will in general correspond to the conditions used in purely thermal operations with respect to the same type of operations,

Our invention is also useful in connection with catalytic cracking processes in which a stationary or moving solid catalyst is used, as for example comminuted co-precipitated alumina-silica and fuller's earth. The mercury-aliphatic halide mixture accelerates solid catalyst reactions in the same manner that it will accelerate conversion of the hydrocarbons in the absence of the solid catalyst.

Although we prefer to us aliphatic halides that vaporize without appreciable decomposition, our invention contemplates the use also of those halides which do decompose appreciably at vaporization temperature but when using such halides we prefer to inject them directly into the reactor 23 without prior vaporization.

We claim:

1. The method of cracking hydrocarbons of 3 or more carbon atoms per molecule at temperatures ranging from 700 to 1400 F. which comprises contacting the hydrocarbons at cracking temperature with a small amount of mercury and a volatile aliphatic halide under pressure conditions such as to maintain the mercury and ali- #4 was then made with mercury at 600 C. and 75 phatic halide in vapor state.

2. The method of cracking hydrocarbons of 3 or. more carbon atoms per molecule which comprises subjecting said hydrocarbons to tempera tures sufiiciently high to'produce cracking in the absence of a solid catalyst, in the presence of a small amount of mercury vapor and aliphatic halide vapor.

3. The method of cracking in accordance with clglgz 2 in which the aliphatic halide is ethyl 1o 1 e.

'2. e method of cracking hydrocarbons of 3 or more carbon atoms per molecule which comprises mixing said hydrocarbons with a small amount of vaporized mercury, heating the mix ture to reaction temperature and then mixing the mixture with a small amount of aliphatic halide.

5. Method in accordance with claim 4 in which the aliphatic halide is injected into the heated mixture at spaced points in the reaction zone.

6. The method of cracking hydrocarbons which 3 comprises subjecting said hydrocarbons to cracking in the presence of mercury and an aliphatic halide under conditions of temperature and pressure at which mercury and the aliphatic halide are in the vaporized state.

7. Method in accordance with claim 6 in which the amount of mercury and alkyl halide in the reaction mixture is from 0.1 to 10 mole percent of each based on the hydrocarbons in the mixture.

H. 0. FOLEINS.

OARLISLE M. THACKER. 

